Microfluidic devices, systems and methods have been gaining acceptance as potentially providing a quantum leap forward in analytical chemical and biochemical processes. In particular, these systems have generally offered the promise of miniaturization, integration and automation to processes that have previously been performed using techniques that have not substantially changed in decades.
To a large extent, the advance of microfluidic technology has been due, at least in part, to the microfabrication technologies as used in the electronics industry, that are used to fabricate intricate networks of microscale channels and chambers in solid substrates. The field has also benefited substantially from development of methods, devices and systems for precisely controlling the movement and direction of fluids, and other materials within these channel networks.
Early researchers focused efforts on minimizing control elements from the macroscale world, e.g., valves, pumps, etc. While these developments were interesting from a technical standpoint, they presented numerous additional problems associated with the cost and complexity of manufacturing those elements.
In the mid 90s, integrated electrokinetic control of fluid or other material movement was developed, which gave rise to the xe2x80x9cvirtual valvexe2x80x9d concept. In brief, through the controlled application of electric fields, one could precisely control the movement of fluids or other materials through interconnected channel structures. These methods generally relied upon the convergence of electric fields at an intersecting point to dictate which components would flow into the intersection, and what the relative quantities of those components would be.
While these pioneering developments were fundamental to the inception of the microfluidics industry, the first commercial versions of these systems typically required flowing materials in each of the various channels that were communicating at common intersection points or channel regions. In a number of particular applications, it would be generally desirable to more definitively control material flow in interconnected channels. For examples, in some cases, it would be desirable to entirely arrest the flow of material along a particular channel, while allowing continued flow in another cannel that is in communication with the first. Further, it would be desirable to obtain these control aspects, without having to include complex structures, such as mechanical valves, pumps, or the like. The present invention meets these and a variety of other important needs.
The present invention is generally directed to methods, devices and systems that utilize non-mechanical valves for use in microfluidic channel systems. Thus, in at least a first aspect, the invention provides a method of controlling material flow in a microscale channel. In accordance with this method, a first channel segment is provided that has first and second ends. A second channel segment is also provided communicating with the first channel segment at a first fluid junction, the first fluid junction being disposed between the first and second ends of the first channel segment. A third channel segment is additionally provided communicating with the first channel segment at a second fluid junction, the second fluid junction being disposed between the first fluid junction and the second end of the first channel segment. A differential driving force is applied between the first and second ends of the first channel segment. In addition, a second differential driving force is applied through the second channel segment that is sufficient to substantially eliminate a differential driving force between the first end of the first channel segment and the first fluid junction, while a third differential driving force is selectively applied through the third channel segment sufficient to substantially eliminate a differential driving force between the second fluid junction and the second end of the first channel segment.
In a related aspect, valve modules are provided, e.g., in microfluidic devices and systems, that include, for example, the channel elements set forth above, in combination with a flow controller that is coupled to at least one end of the first channel and also coupled to the second and third channels. The flow controller is set to apply the first, second and third driving forces set forth above to operate the valve module.